Source Analysis And Risk Assessment Of Soil Heavy Metals In A Lead-zinc Mining Area

In recent years,Soil is an important containment medium for heavy metals,and its pollution problem is becoming more and more serious.If it is not controlled,it will cause major harm to the ecological environment and human health.Among various pollutants,heavy metal pollution has received widespread attention due to its wide-ranging sources,diverse forms,complex migration and transformation,and difficulties in repair and treatment.To solve the problem of heavy metal pollution in soil,the first task is to Clarify ts pollution status and characteristics,determine its pollution source.So as to control it from the source in a targeted manner.In this paper,37 sampling points were set up in a Pb-Zn mining area,and soil samples were collected to test the concentrations of eight metals,including Cr,Mn,Ni,Cu,Zn,As,Cd and Pb.The spatial distribution of heavy metals in the mining area is analyzed by the Arg GIS Kriging interpolation method,to explore the distribution pattern of each heavy metal,and factor analysis and UNMIX model were used to analyze the possible sources of heavy metals in the study area.The results of the source analysis were verified with each other to obtain the most reasonable source analysis results Finally,through the potential ecological hazard index method and pollution loss model,combined with the results of pollution source analysis,a comprehensive evaluation of the local farmland soil environmental quality was carried out.he following main conclusions were reached:(1)The average values of heavy metal elements As and Cd in the soil of the mine area are higher than the risk screening value of the"Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard"(GB15618-2018).In the vertical distribution,the As element exceeds the standard of the heavy metal elements detected most seriously.Pb,Cd,Cu,Ni,etc.also have different degrees of excess in the vertical distribution of tailings pond soil.In terms of spatial distribution,the overall content of As element is relatively high.In addition,Pb,Cd,Cu,and Ni in the tailing pond and surrounding soil also exceed the standard in varying degrees in space.(2)The factor analysis method,PMF model method and UNMIX model method all have three main factors,representing agricultural pollution sources such as fertilizer application and pesticide use,human activity sources such as slag accumulation,and soil parent material sources.The contribution rates of the three factors of the factor analysis method were 38.93%,29.72%,and 23.99%;the contribution rates of the three factors of the PMF model method were 25.26%,31.69%,and 43.15%;the contribution rates of the three sources were analyzed by the UNMIX method They are 29.22%,15.81%,and 55.25%respectively.Using the Unmix model to perform regression analysis on the correlation between the measured and predicted values of Total,it can be seen that there is a good linear relationship between the measured and predicted values of Total(R~2=0.999),and the simulation effect of the measured and predicted values of each heavy metal is better.(3)The Nemeiro comprehensive pollution index method evaluates that the Cr,Ni,Cu element pollution index in the mining area is in a safe state;the average sin gle factor pollution index of Pb element is in a light pollution state;the average single-factor pollution of Mn and Zn elements If the index is greater than 2,which is in a moderately polluted state,and the average single-factor pollution index of As and Cd elements is greater than 3,and it is in a severely polluted state;the geo-accumulation index method evaluates the pollution degree of the eight heavy metals in the soil of the mining area in order:As>Cd>Zn>Mn>Pb>Cu>Ni>Cr,the pollution degree of As is the most serious;through the comprehensive assessment of potential ecological hazard index method,the average Er value of the six heavy metals in the mining area is in the order of As>Cd>Pb>Cu>Zn>Cr.As and Cd are the two most important contributing factors to ecological risk.As has the highest contribution rate to the potential ecological risk index,reaching 55.6%;Cd is second with a contribution of 38.93%,and the sum of the contribution rates of the remaining eight heavy metals to the comprehensive potential ecological risk index was 5.47%.The results of the application of the pollution loss model show that the pollution loss rate of 37 sampling points is between 0.70%and 78.10%,with an average of 16.35%,and the overall level is in the third level.The evaluation results of Nemeiro comprehensive pollution index method,geo-accumulation index method,potential ecological risk index method and pollution loss evaluation are basically the same,and it is concluded that the pollution and potential ecological risks of As and Cd were relatively highest.